A phased array antenna system may be used to generate one or more beams, which are steerable and shapeable. In many instances, traveling-wave-tube amplifiers (TWTs) are used with passive antennas to generate shaped or spot beams. With evolving semiconductor technologies and improvements in yield, cost, and reliability of solid-state technologies, phased array systems with solid-state power amplifier (SSPA) elements have become realizable for satellite communications systems.
A multiple-beam, transmit phased array antenna system typically includes a plurality of beam drivers, power dividers, and beamformer modules. In addition, in order to combine the signals associated with the multiple beams, the beamformer modules also include a combiner network (e.g., a Wilkinson combiner network), which combines the individually phase weighted beam signals, and provides composite signals to a plurality of amplifier modules and radiating elements.
Many of these antenna components are interconnected using radio frequency (RF) interconnects (e.g., coaxial interconnects), direct current (DC) interconnects, and control signal interconnects. The structure and arrangement of interconnects depend on the type of phased array antenna configuration. Phased array antenna systems are known to use a multitude of connectors and cables to interconnect system elements.
Two basic types of phased array antenna configurations have been used. These basic types include a “tile” array antenna and a “brick” array antenna. A tile configuration places the element electronics in a tile-like arrangement in the plane of the radiating aperture and mounted on a printed wiring board (PWB) containing the RF, DC, and control signal distribution networks. A brick configuration places the element electronics in an upright position located beneath the plane of the radiating aperture. The radiating elements, associated electronics, and supporting structure are typically divided into rows, as is illustrated in FIG. 1.
FIG. 1 illustrates an exploded view of a multiple-layer PWB 100 associated with a tile array antenna. PWB 100 includes a Wilkinson divider network 102, a plurality of amplifier modules 104, and a plurality of radiating elements 106 mounted in a tile array configuration on a surface 110 of PWB 100. Incoming signals 112 from beam driver amplifiers (not illustrated) are divided by Wilkinson divider network 102 into a number of signals that corresponds to the number of radiating elements 106. Each signal is then amplified by an amplifier module 104, which includes an SSPA. Each amplified signal is then provided to a radiating element 106, which produces an electromagnetic wave that travels generally in direction 114 (e.g., the bore-sight of the antenna). A multi-beam array contains a beam driver amplifier and Wilkinson divider network for every beam. The beams are then combined using a Wilkinson combiner network, and the composite signal is then provided to the amplifier module. In conventional tile array systems, amplifier modules 104 are oriented perpendicularly to the bore-sight of the antenna.
Although phased array systems having a tile array configuration may include fewer cables and connectors than their brick counterparts, tile array systems have several negative aspects. First, because amplifier modules 104 are oriented perpendicularly to the bore-sight of the antenna, the physical dimensions of the amplifier modules 104 are limited to the lattice spacing of the array (e.g., the distance between radiating elements 106). The lattice spacing of an array decreases as the frequency of operation increases, and accordingly, the physical dimensions of the amplifier modules 104 should become smaller as the frequency of operation increases. For example, a typical phased array system may have approximately 0.5λ lattice spacing in order to provide reasonable grating-lobe free performance, where λ is the free-space wavelength of the RF signal. At higher operating frequencies (e.g., frequencies at or higher than Ku-band frequencies), the lattice spacing may be so small that an amplifier module having sufficiently small dimensions may not be readily manufacturable using current semiconductor manufacturing technologies.
In addition, a large number of layers (e.g., 28 or more) may be used to implement the Wilkinson combiner network 102, power lines, control lines, and radiating elements 106. Because numerous vias and transmission lines are present within the layers, a significant likelihood exists that one or more defective vias or transmission lines may be present within a newly manufactured PWB. Also, in the case of a transmission line or via failure, reworking the PWB may be difficult or impossible. Accordingly, manufacturing yields may be relatively low, particularly in PWBs that support large arrays (e.g., arrays with hundreds or thousands of radiating elements).
Another negative aspect of a tile array configuration relates to dissipating heat through the PWB layers. For some phased array systems, high power levels (e.g., 2-8 Watts (W)) may be required from each amplifier module (e.g., each SSPA). Because PWB materials generally are poor heat conductors, intolerable thermal gradients may be produced within the PWB layers proximate to the amplifier modules.
A brick array configuration for a phased array antenna system provides an alternative to a tile array configuration. A brick array configuration also includes a planar structure, upon which an array of radiating elements is positioned. An array of amplifier modules and a Wilkinson combiner network are located beneath the planar structure. However, the amplifier modules are arranged in parallel with the bore-sight of the antenna. Accordingly, a brick array configuration has an advantage over a tile array configuration in that the amplifier modules of the brick array configuration are not entirely limited by the lattice spacing of the radiating elements. Accordingly, a brick array configuration may be adapted to operate at higher frequencies than a tile array configuration.
However, a negative aspect of a brick array configuration is that it includes a large number of RF cable/connector types of interconnects. These interconnects are costly, difficult to assemble, and add a significant amount of weight to the system. Further, the connectors are susceptible to becoming dislodged in high-vibration situations (e.g., during launch of a spacecraft).
It is desirable to provide phased array systems, apparatus, and methods, which may be operated at relatively high frequencies, and which may have improved thermal performance, manufacturing yield, weight, reliability, and/or cost. Other desirable features and characteristics of embodiments of the inventive subject matter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.